Device and process for limiting idling fuel in carburetors

ABSTRACT

A polyamide cap fits tightly over the head of the idling needle and a vane on the cap abuts a boss on the carburetor body to prevent needle rotation in one direction. Internal teeth of the cap fit over the idling needle head to prevent separating the cap from the needle, while lands on the interior of the cap permit easy installation. The cap is installed during carburetor flow testing with the idling needle in the position producing the maximum allowable amount of fuel flow through the idling passages and with the vane contacting a boss on the side preventing further increases in the amount of idling fuel. A decrease in idling fuel can be effected by rotating the cap and needle in the direction moving the vane away from the boss for almost one full turn.

United States Patent [72] inventor William W. Charron Livonia, Mich.

[211 AppLNo. 661,570

[22] Filed Aug. 18, 1967 [45] Patented Nov. 9, 1971 [73] Assignee Ford Motor Company Dearborn, Mich.

[54] DEVICE AND PROCESS FOR LIMITING IDLING 41.4, 66, 41, 71, DIG. 38; 29/447; 264/342; 137/385, 382, 382.5; 251/89, 92, 93,112,274, DIG. 4,115, 214, 20, 266, 291, 289; 239/366 [56] References Cited UNITED STATES PATENTS 1,801,396 4/1931 Thatchen 29/447 UX 1,872,786 8/1932 Mock eta1.. 261/41 (.4) 2,618,473 11/1952 Whitford.... 261/41(.4)' 2,858,570 11/1958 Richards 264/342 X 3,132,412 5/1964 Kneissig 264/342 X 3,166,292 l/l965 Forman 261/66 X 3,285,312 ll/1966 Dison et al 137/385 X 3,321,195 5/1967 Korte 261/41 (.4) 1,272,036 7/1908 Greuter 261/71 3,414,244 12/1968 Patterson, .lr. 261/41 2,551,117 5/1951 Gortner 287/53 H 2,544,111 3/1951 Schneebeli 261/71 X 2,590,217 3/1952 Snyder et a1. 261/71 X 2,816,573 12/1957 Kaddis et a1. 261/41 X 3,188,062 6/1965 Reid et a1 261/41 3,455,513 7/1969 Wyse 239/366 Primary Examiner-Ronald R. Weaver Attorneys-John R. Faulkner and Glenn S. Arendsen ABSTRACT: A polyamide cap fits tightly over the head of the idling needle and a vane on the cap abuts a boss on the carburetor body to prevent needle rotation in one direction. internal teeth of the cap fit over the idling needle head to prevent separating the cap from the needle, while lands on the interior of the cap permit easy installation. The cap is installed during carburetor flow testing with the idling needle in the position producing the maximum allowable amount of fuel flow through the idling passages and with the vane contacting a boss on the side preventing further increases in the amount of idling fuel. A decrease in idling fuel can be effected by rotating the cap and needle in the direction moving the vane away from the boss for almost one full turn.

PATENTEDNUV 9 I97! W/LL/AM W C/MRRON INVENTO a. I flaw JMW ATTORNEYS DEVICE AND PROCESS FOR LIMITING IDLING FUEL IN CARBURETORS SUMMARY OF THE INVENTION Recently adopted exhaust emission standards specify the maximum proportions of unburned hydrocarbons and certain other compounds in the exhaust gases of internal combustion engines. The amount of fuel supplied to an engine through the idling passages afi'ects directly the amount of undesirable exhaust emissions during engine idling. With proper calibration of the idling system during carburetor assembly, most emission standards can be met; however, an increase in the amount of idling fuel during subsequent engine or vehicle assembly operations or by field service personnel could increase the undesirable emission beyond the standards.

In the past, setscrews have been used to lock the idling control needle in a certain position Of course, the setscrews can be loosened to permit a change and then retightened with the change being impossible to detect without another calibration or an exhaust gas sampling. Furthermore, the setscrews must be loosened and retightened whenever the amount of idling fuel is adjusted for changes in engine requirements necessitated by varying climate, weather, ground elevation, or engine conditions.

The idling fuel limiting device provided by this invention does not interfere with minor adjustments to the idling fuel system while providing positive evidence of unauthorized tampering with the idling needle to increase the amount of idling fuel beyond the calibrated amount. In a device for metering fuel to an internal combustion engine that has a rotatable member for increasing and decreasing the amount of idling fuel, the limiter comprises a cap made of a hard but deformahle material fitting on the head of the rotatable member so the cap is nonrotatable relative thereto. A projecting vane is formed on the exterior of the cap where it contacts a rigid portion of the body when rotation of the member in the direction increasing the amount ofidling fuel is attempted.

Preferably the cap contains internal teeth fitting over the head of the threaded member, the idling needle in most conventional carburetors, with a force sufficient to prevent integral removal of the cap. Lands are formed on the interior of the cap to guide the cap on the head during installation.

The cap is installed after carburetor assembly while the carburetor is being flow tested. Just prior to cap installation, the idling needle is backed out to the position where the amount of idling -fuel is predetermined maximum providing engine compliance with the emission legislation. The cap then is pressed on the head of the idling needle with the vane on the cap abutting projection from the carburetor body on the side preventing further increases in the amount of idling fuel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an exploded view ofa cap and needle with a portion of the cap sectioned to show the internal teeth and lands. FIG. 2 is a sectioned elevation of a portion of a carburetor showing the cap installed on an idling needle with the needle installed in the carburetor body.

DETAILED DESCRIPTION Referring to FIG. 1, the cap represented by the numeral has a vane 12 formed on the exterior surface. Cap 10 preferably is made of polymeric material capable of surviving in the underhood compartment of a vehicle. Polyamides are desirable cap materials because soakingthe polyamide cap in water softens it to ease assembly. After assembly, the polyamide cap dries to become sufficiently tough toinhibit removal and sufficiently brittle to spit instead of yielding to a determined removal procedure. The interior of the cap contains four tapered lands, one of which is represented by numeral 14, evenly spaced and alternating with four inwardly projecting teeth, two of which are represented'by numerals 16 and 18. The inner surfaces of the teeth define a substantially radial plane while the outer surfaces taper to the interior wall of the cap. Cross slots 20 and 22 for receiving a screwdriver blade are molded in the closed end of cap 10.

Numeral 24 designates the carburetor idling needle. Needle 24 has a tapered point 26, a threaded body 28, and an enlarged head '30. A plurality of closely spaced axial slots 32 are cut into the cylindrical surface of head 30. The surface of head 30 facing body 28 is a'substantially radial plane. A radial slot 34 for receiving a screwdriver blade is formed in the outer radial surface of head 30.

Turning to FIG. 2, a carburetor 36 contains an induction passage 38 with a throttle blade 40 mounted therein. An idling fuel passage 42 is connected to a fuel source (not shown) and communicates through a port 44 with the induction passage 38 posterior to throttle blade 40. Idling needle 24 is threaded into a hole through the carburetor body coaxial with port 44. Cap 10 is pressed onto head 30 so teeth l6, 18, etc. pass over the cylindrical surface thereof and-snap into contact with the radial surface between the head and the body. Vane l2 abuts a projection 46 extending outward from the carburetor body.

During carburetor manufacturing, the carburetor is assembled completely except for installation of the cap on the idling needle. The carburetor is placed on a flow test stand and the idle needle is adjusted to provide the maximum amount of flow through the idling passage at which the engine ultimately using the carburetor will comply with exhaust emission standards. Then a polyamide cap, which has been soaked in water to soften it slightly, is pressed on the head of the idling needle with the vane abutting the boss on the side preventing further increases in the amount of fuel flow. For a needle having conventional right-hand threads, this abutment is on the right side of a boss located above the needle as shown in the drawing.

Lands 14 combine with the sloping outer surfaces of the teeth to guide the cap over the head of the idling screw until the teeth snap over the head into the position shown in FIG. 2. Once this occurs, the lands coact with the axial slots in the cylindrical surface of the needle head to inhibit relative rotation between the cap and the needle.

Needle 24 now can be rotated inward to reduce the amount of idling fuel but cannot be rotated outward to increase the idling fuel flow beyond the predetermined maximum. Lands l4 grip the cylindrical surface of head 30 tightly so there is not need to line up the slots 20 or 22 with slot 34 since the capneedle assemblycan be rotated either by hand or by inserting a screwdriver in the slots in the cap. It is preferable for lands 14 to interfere with head 30 sufficiently to remove cap material during or produce plastic deformation after installation. Other. useful polymeric cap materials include the phenolics, polyurethanes, polyacrylates, and the synthetic rubber materials.

During further carburetor processing the absorbed water in the polyamide cap material evaporates and the cap becomes relatively brittle. Any subsequent attempts to remove the cap generally result in splitting the cap along axial planes so the cap cannot be reinstalled. A visual inspection of the carburetor then readily reveals the tampering.

Thus, this invention provides an idle limiting device that is easily installed but cannot be removed without leaving clear evidence of tampering The device is useful carburetors of different types with the only requirement being an abutment for the vane. In many cases, an existing portion of the carburetor body can be used as the abutment; alternatively, a boss can be formed on the carburetor body specifically for this purpose as shown in the drawing. Installing the cap during flow testing insures adequate fuel flow despite tolerance variations in metering jets and other flow control components.

Iclaim: j

1. In a device having a body for metering fuel to an internal combustion engine and having a rotatable member for increasing the amount of idling fuel, an idling fuel limiter comprising a head formed on the rotatable member, said head being located just outside the body of said device, and

a cap made of a deformable material and movable onto said head, said cap fitting on the head so said cap is nonrotatable relative to the head, said cap containing internal teeth that deform to permit moving the cap over said head, said mitting rotation in the direction decreasing the amount of idling fuel.

2. The device of claim 1 comprising lands formed on the interior of the cap to guide the teeth over the head during instalteeth fitting over said head to prevent integral removal of 5 lation of the cap on the head the cap from the head, said cap having an exterior projecting vane located to prevent rotation of the member in the direction increasing the amount of idling fuel but per- 3. The device of claim 2 in which the cap is made of a polyamide.

i l l l i 

1. In a device having a body for metering fuel to an internal combustion engine and having a rotatable member for increasing the amount of idling fuel, an idling fuel limiter comprising a head formed on the rotatable member, said head being located just outside the body of said device, and a cap made of a deformable material and movable onto said head, said cap fitting on the head so said cap is nonrotatable relative to the head, said cap containing internal teeth that deform to permit moving the cap over said head, said teeth fitting over said head to prevent integral removal of the cap from the head, said cap having an exterior projecting vane located to prevent rotation of the member in the direction increasing the amount of idling fuel but permitting rotation in the direction decreasing the amount of idling fuel.
 2. The device of claim 1 comprising lands formed on the interior of the cap to guide the teeth over the head during installation of the cap on the head.
 3. The device of claim 2 in which the cap is made of a polyamide. 